JCB 3CX backhoe

mrbrendank

i have a jcb 3cx backhoe, 1986. on the backhoe i see that it can be extended but i cannot find out how, there is a pedal on the floor which i think extends it but when it is pressed nothing happens. it seems to be piped up and everything so i havent a clue where to start, any ideas?

Thanks

Nekarsulm

Couple of things. Is the pedal its-self bending instead of moving the valve under the cab? Can happen.
When you press the pedal, does the engine go under load? Can you hear/feel it labouring?
If so, have you repositioned the big locking pin that prevents the extra-dig arm extending?
Ist half way up the dipper arm, big pin about an inch and a half thick, should be retained by a very big "R" pin. Pull out R pin, lift the locking/retaining pin up, and there is a second set of holes in the locking pin to replace the R pin in.

mrbrendank

Nekarsulm wrote: »

Couple of things. Is the pedal its-self bending instead of moving the valve under the cab? Can happen.
When you press the pedal, does the engine go under load? Can you hear/feel it labouring?
If so, have you repositioned the big locking pin that prevents the extra-dig arm extending?
Ist half way up the dipper arm, big pin about an inch and a half thick, should be retained by a very big "R" pin. Pull out R pin, lift the locking/retaining pin up, and there is a second set of holes in the locking pin to replace the R pin in.

thanks for that. i see the pin alright, the boom ram is out now getting a seal replaced so as soon as i have it done i will give that a try. what is the purpose of that pin? like if i get it out is it ok to leave out?

Nekarsulm

I think its primarily to stop you using the back arm as a crane, and overloading things. You could find yourself lifting a half ton bag of fertilizer, and the temptation is there to extend the arm to get a bit more reach to place the bag somewhere. Easy to tip a digger over at that crack, and you would be exceeding the rated safety limits anyway.
Stops the extending boom slowly dropping/extending when the digger is parked up as well.
(would take a week or two to go all the way to the ground, normally).

mrbrendank

Nekarsulm wrote: »

I think its primarily to stop you using the back arm as a crane, and overloading things. You could find yourself lifting a half ton bag of fertilizer, and the temptation is there to extend the arm to get a bit more reach to place the bag somewhere. Easy to tip a digger over at that crack, and you would be exceeding the rated safety limits anyway.
Stops the extending boom slowly dropping/extending when the digger is parked up as well.
(would take a week or two to go all the way to the ground, normally).

from what i can see the pin is in the right place?

911s

mrbrendank wrote: »

from what i can see the pin is in the right place?

Sometimes the pedal is used to power a hammer
circuit, with a changeover valve. Check if you have extra pipes for a hammer, clamped to boom.

Nekarsulm

mrbrendank wrote: »

from what i can see the pin is in the right place?

Pin doesn't look like it moved in a long time. Its in the "unlocked position" all right.

+1 on 911s comment above.

mrbrendank

no pipes on the boom anyway. i followed the pipes from the ram and they lead back to the valve chest under the pedal alright. since i got the pedal free and moving i have had an issue with the jcb cutting out, like as if there was too much labouring going on. so something might be going somewhere it shouldnt.

mrbrendank

quick question lads, i got the ram in today and got it started, there seems to be very little power in the backhoe, regarding digging, it seems very weak, i have the throtle up past half way. now the next thing i have to replace is the spool valves on the front chest valve block, as they piss oil when the jcb is started, would the front chest block leaking effect the power to the backhoe?

mrbrendank

Nekarsulm wrote: »

Pin doesn't look like it moved in a long time. Its in the "unlocked position" all right.

+1 on 911s comment above.

ok so it was just me..
the front valve block was leaking so i changed that today, and that fixed it. pedal activates the extension on the arm now and a little more power in the rear arm too so im happy out. thanks for your help anyway

Nekarsulm

There is what JCB call an "Unloader" valve alongside the front loader valve block, I never had to touch it, but seemingly it can cause lack of pressure to the back arm.
Back arm should be well able to lift the back off the machine straight up in the air, and throw it around.
Had you much trouble resealing the valve block?
Is your one a HUSCO brand block?

https://m.youtube.com/#/watch?v=SPaOBy25FmQ

https://m.youtube.com/#/watch?v=Z1uzuwwPVt4

fergal85

I just got an 1984 jcb 3cx. Looks like it was piped for breaker before but the change over handle is stuck and i presume thats why they removed the piping. Any know if its a big job to fix?

mrbrendank

Nekarsulm wrote: »

There is what JCB call an "Unloader" valve alongside the front loader valve block, I never had to touch it, but seemingly it can cause lack of pressure to the back arm.
Back arm should be well able to lift the back off the machine straight up in the air, and throw it around.
Had you much trouble resealing the valve block?
Is your one a HUSCO brand block?

https://m.youtube.com/#/watch?v=SPaOBy25FmQ

https://m.youtube.com/#/watch?v=Z1uzuwwPVt4

thanks fot that, would you by any chance of a photo of this unloader valve? i lifted the digger today with the back arm no problem, the issue i have with the boom is it is very slow to turn left and right and up. everything else is fine. so i am thinking maybe an adjustment of this unloader valve might do it?

what are them youtube links? they just bring me to youtube

Nekarsulm

I think a faulty unloader would take power from all the functions. I'll look for a picture anyway.
Take a look at the rigid steel lines going to the slew pots, one or both haven't got hammered flat by any chance?

mrbrendank

Nekarsulm wrote: »

I think a faulty unloader would take power from all the functions. I'll look for a picture anyway.
Take a look at the rigid steel lines going to the slew pots, one or both haven't got hammered flat by any chance?

checked that today alright but they seem good. i have the throtle around half way. should it be any higher than that maybe?